The invention relates to a method for controlling an ultrasonic unit of an ultrasonic cleaning system.
Ultrasonic cleaning systems for professional removal of tartar and/or plaque are sufficiently known in the art. These systems feature an instrument that is movably provided in a hand-held unit and that can be set in oscillation by means of an ultrasonic unit provided in the hand-held unit. There are two types of ultrasonic units: piezoelectric and magnetostrictive.
In piezoelectric ultrasonic units the oscillation is generated by the influence of AC voltage on a quartz crystal. Magnetostrictive ultrasonic units comprise an electromagnetic converter unit with a coil unit, by means of which an electric control signal generated in a control unit is converted into mechanical oscillation. For this purpose, a ferromagnetic core element is inserted into the electromagnetic converter unit and the coil unit is energized by the electric control signal.
The electric control signal is an AC signal that produces a magnetic alternating field in the coil unit. The magnetic alternating field creates a periodic length change of the ferromagnetic core element in the form of a mechanical oscillation (“ultrasonic sound”). For transferring the mechanical oscillations to the instrument, the ferromagnetic core element is connected with the instrument by means of mechanical coupling.
Based on the dimensions of the electromagnetic converter unit and of the coil unit, a resonant frequency is generated for the respective electromagnetic converter unit, resulting in periodic oscillations with a maximum amplitude in the ferromagnetic core element. The periodic oscillations occur in the case of resonance as a stationary wave and are transmitted to the instrument connected to the ultrasonic unit, for example a working tip. To ensure that the electromagnetic converter unit achieves the maximum possible power output, it is necessary to operate it in resonance. The resonant frequency of the converter unit is dependent on numerous marginal conditions that frequently change during operation of the ultrasonic cleaning system and necessitate retuning of the resonant frequency.
It is an object of the present invention is to present a method for controlling an ultrasonic unit of an ultrasonic cleaning system, which with maximum power output enables easy operation and patient-friendly functioning of the ultrasonic cleaning system.